Fullfører oppgave 19.1: Canvas-primitiv Svelte-komponent

Implementerer det felles canvas-underlaget som whiteboard, storyboard
og fremtidige canvas-views skal bruke. Ren Svelte 5 komponent uten
backend-avhengigheter.

Funksjoner:
- Pan/zoom kamera med CSS transforms (transform-origin: 0 0)
- Viewport culling med 200px margin for smooth scrolling
- Pointer events (unified mus + touch)
- Pinch-zoom og to-finger-pan for touch
- Snap-to-grid (toggle med G-tast eller toolbar)
- Fullskjermsmodus (fixed positioning)
- Lasso-seleksjon og shift+klikk multi-select
- Edge-pan ved drag nær kanter
- Responsivt: 44px touch targets på mobil, tilpasset toolbar
- zoomToFit() for å sentrere alle objekter
- Consumer-rendering via Svelte 5 snippets

Filer:
- frontend/src/lib/components/canvas/Canvas.svelte
- frontend/src/lib/components/canvas/types.ts
- frontend/src/lib/components/canvas/index.ts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/features/canvas_primitiv.md

@@ -190,10 +190,14 @@ Storyboard-consumeren bruker `onObjectMove` til å kalle en SpacetimeDB-reducer
 
 ## 10. Implementeringsstrategi
 
-### Fase 1: Kjerne-primitiv
+### Fase 1: Kjerne-primitiv ✅ (implementert)
 - `<Canvas>` Svelte-komponent med kamera (pan/zoom), viewport culling, og objekt-drag
 - Touch-støtte (pinch-zoom, to-finger-pan)
-- BlockShell fullskjerm-toggle
+- Fullskjerm-toggle (i canvas-toolbar, `position: fixed`)
+- **Filer:** `src/lib/components/canvas/Canvas.svelte`, `types.ts`, `index.ts`
+- **Bruk:** `import { Canvas } from '$lib/components/canvas'`
+- **API:** `renderObject` snippet for consumer-rendering, events via props (`onObjectMove`, `onCameraChange`, `onSelectionChange`)
+- **Eksport:** `getCamera()`, `setCamera()`, `zoomToFit()` metoder
 
 ### Fase 2: Storyboard som første consumer
 - `<StoryboardCard>` rendrer meldingsboks-kort på canvaset

frontend/src/lib/components/canvas/Canvas.svelte

@@ -0,0 +1,660 @@
+<script lang="ts">
+	import { type Snippet } from 'svelte';
+	import {
+		type Camera,
+		type CanvasObject,
+		type GridConfig,
+		type ViewportSize,
+		visibleObjects,
+		screenToWorld,
+		snap,
+		clampZoom,
+		ZOOM_MIN,
+		ZOOM_MAX,
+	} from './types.js';
+
+	/**
+	 * Canvas Primitive — felles fritt-canvas underlag.
+	 *
+	 * Håndterer kamera (pan/zoom), viewport culling, objekt-plassering
+	 * og interaksjon. Consumer bestemmer hva som rendres via renderObject snippet.
+	 */
+
+	interface Props {
+		/** Objects to render on the canvas */
+		objects: CanvasObject[];
+		/** Render callback for each visible object */
+		renderObject: Snippet<[CanvasObject]>;
+		/** Grid configuration */
+		grid?: GridConfig;
+		/** Initial camera position */
+		initialCamera?: Camera;
+		/** Callback when an object is moved (drag-drop) */
+		onObjectMove?: (id: string, x: number, y: number) => void;
+		/** Callback when camera changes */
+		onCameraChange?: (camera: Camera) => void;
+		/** Callback when selection changes */
+		onSelectionChange?: (ids: string[]) => void;
+	}
+
+	let {
+		objects,
+		renderObject,
+		grid = { enabled: false, size: 20 },
+		initialCamera = { x: 0, y: 0, zoom: 1.0 },
+		onObjectMove,
+		onCameraChange,
+		onSelectionChange,
+	}: Props = $props();
+
+	// --- State ---
+	let camera = $state<Camera>({ ...initialCamera });
+	let selectedIds = $state<Set<string>>(new Set());
+	let isFullscreen = $state(false);
+	let viewport = $state<ViewportSize>({ width: 0, height: 0 });
+
+	// Interaction state (not reactive — internal bookkeeping)
+	let isPanning = $state(false);
+	let isDragging = $state(false);
+	let isLassoing = $state(false);
+	let spaceHeld = $state(false);
+	let dragTargetId: string | null = null;
+	let dragStartWorld = { x: 0, y: 0 };
+	let dragObjectStart = { x: 0, y: 0 };
+	let panStart = { x: 0, y: 0 };
+	let cameraStart = { x: 0, y: 0 };
+	let lassoStart = { x: 0, y: 0 };
+	let lassoEnd = $state({ x: 0, y: 0 });
+
+	// Touch tracking for pinch-zoom
+	let activeTouches = new Map<number, { x: number; y: number }>();
+	let lastPinchDist = 0;
+	let lastPinchCenter = { x: 0, y: 0 };
+
+	// DOM refs
+	let containerEl: HTMLDivElement | undefined = $state();
+
+	// --- Derived ---
+	let visibleObjs = $derived(visibleObjects(objects, camera, viewport));
+
+	let transformStyle = $derived(
+		`translate(${camera.x}px, ${camera.y}px) scale(${camera.zoom})`
+	);
+
+	let lassoRect = $derived.by(() => {
+		if (!isLassoing) return null;
+		const x = Math.min(lassoStart.x, lassoEnd.x);
+		const y = Math.min(lassoStart.y, lassoEnd.y);
+		const w = Math.abs(lassoEnd.x - lassoStart.x);
+		const h = Math.abs(lassoEnd.y - lassoStart.y);
+		return { x, y, width: w, height: h };
+	});
+
+	// Notify consumers of camera changes
+	$effect(() => {
+		// Access camera fields to create dependency
+		const _ = camera.x + camera.y + camera.zoom;
+		onCameraChange?.(camera);
+	});
+
+	// ResizeObserver for viewport size
+	$effect(() => {
+		if (!containerEl) return;
+		const ro = new ResizeObserver((entries) => {
+			for (const entry of entries) {
+				viewport.width = entry.contentRect.width;
+				viewport.height = entry.contentRect.height;
+			}
+		});
+		ro.observe(containerEl);
+		return () => ro.disconnect();
+	});
+
+	// Keyboard listeners
+	$effect(() => {
+		function onKeyDown(e: KeyboardEvent) {
+			if (e.code === 'Space' && !e.repeat) {
+				spaceHeld = true;
+				e.preventDefault();
+			}
+			if (e.code === 'Escape' && isFullscreen) {
+				isFullscreen = false;
+			}
+			// 'g' toggles grid snap
+			if (e.code === 'KeyG' && !e.ctrlKey && !e.metaKey) {
+				grid = { ...grid, enabled: !grid.enabled };
+			}
+		}
+		function onKeyUp(e: KeyboardEvent) {
+			if (e.code === 'Space') {
+				spaceHeld = false;
+			}
+		}
+		window.addEventListener('keydown', onKeyDown);
+		window.addEventListener('keyup', onKeyUp);
+		return () => {
+			window.removeEventListener('keydown', onKeyDown);
+			window.removeEventListener('keyup', onKeyUp);
+		};
+	});
+
+	// --- Zoom ---
+	function handleWheel(e: WheelEvent) {
+		e.preventDefault();
+		const zoomFactor = e.deltaY > 0 ? 0.92 : 1.08;
+		zoomAt(e.clientX, e.clientY, zoomFactor);
+	}
+
+	function zoomAt(screenX: number, screenY: number, factor: number) {
+		const rect = containerEl?.getBoundingClientRect();
+		if (!rect) return;
+		const cx = screenX - rect.left;
+		const cy = screenY - rect.top;
+
+		const newZoom = clampZoom(camera.zoom * factor);
+		const scale = newZoom / camera.zoom;
+
+		camera = {
+			x: cx - scale * (cx - camera.x),
+			y: cy - scale * (cy - camera.y),
+			zoom: newZoom,
+		};
+	}
+
+	// --- Pointer events ---
+	function handlePointerDown(e: PointerEvent) {
+		if (!containerEl) return;
+		const rect = containerEl.getBoundingClientRect();
+		const sx = e.clientX - rect.left;
+		const sy = e.clientY - rect.top;
+
+		// Middle button or space+left = pan
+		if (e.button === 1 || (e.button === 0 && spaceHeld)) {
+			isPanning = true;
+			panStart = { x: e.clientX, y: e.clientY };
+			cameraStart = { x: camera.x, y: camera.y };
+			containerEl.setPointerCapture(e.pointerId);
+			e.preventDefault();
+			return;
+		}
+
+		// Left button on object = drag object
+		if (e.button === 0) {
+			const target = (e.target as HTMLElement).closest('[data-canvas-object-id]');
+			if (target) {
+				const id = target.getAttribute('data-canvas-object-id')!;
+				isDragging = true;
+				dragTargetId = id;
+				const world = screenToWorld(sx, sy, camera);
+				dragStartWorld = { x: world.x, y: world.y };
+				const obj = objects.find(o => o.id === id);
+				if (obj) {
+					dragObjectStart = { x: obj.x, y: obj.y };
+				}
+
+				// Selection logic
+				if (e.shiftKey) {
+					const newSet = new Set(selectedIds);
+					if (newSet.has(id)) newSet.delete(id);
+					else newSet.add(id);
+					selectedIds = newSet;
+				} else if (!selectedIds.has(id)) {
+					selectedIds = new Set([id]);
+				}
+				onSelectionChange?.([...selectedIds]);
+
+				containerEl.setPointerCapture(e.pointerId);
+				e.preventDefault();
+				return;
+			}
+
+			// Left button on empty space = lasso or deselect
+			if (!spaceHeld) {
+				if (e.shiftKey) {
+					// Start lasso
+					isLassoing = true;
+					lassoStart = { x: sx, y: sy };
+					lassoEnd = { x: sx, y: sy };
+				} else {
+					// Deselect all
+					selectedIds = new Set();
+					onSelectionChange?.([]);
+				}
+				containerEl.setPointerCapture(e.pointerId);
+				e.preventDefault();
+			}
+		}
+	}
+
+	function handlePointerMove(e: PointerEvent) {
+		if (!containerEl) return;
+
+		if (isPanning) {
+			const dx = e.clientX - panStart.x;
+			const dy = e.clientY - panStart.y;
+			camera = {
+				...camera,
+				x: cameraStart.x + dx,
+				y: cameraStart.y + dy,
+			};
+			return;
+		}
+
+		if (isDragging && dragTargetId) {
+			const rect = containerEl.getBoundingClientRect();
+			const sx = e.clientX - rect.left;
+			const sy = e.clientY - rect.top;
+			const world = screenToWorld(sx, sy, camera);
+			let newX = dragObjectStart.x + (world.x - dragStartWorld.x);
+			let newY = dragObjectStart.y + (world.y - dragStartWorld.y);
+
+			if (grid.enabled) {
+				newX = snap(newX, grid.size);
+				newY = snap(newY, grid.size);
+			}
+
+			onObjectMove?.(dragTargetId, newX, newY);
+
+			// Edge-pan: scroll canvas when dragging near edges
+			const edgeMargin = 40;
+			const edgeSpeed = 8;
+			let panDx = 0, panDy = 0;
+			if (sx < edgeMargin) panDx = edgeSpeed;
+			if (sx > rect.width - edgeMargin) panDx = -edgeSpeed;
+			if (sy < edgeMargin) panDy = edgeSpeed;
+			if (sy > rect.height - edgeMargin) panDy = -edgeSpeed;
+			if (panDx || panDy) {
+				camera = { ...camera, x: camera.x + panDx, y: camera.y + panDy };
+			}
+			return;
+		}
+
+		if (isLassoing) {
+			const rect = containerEl.getBoundingClientRect();
+			lassoEnd = { x: e.clientX - rect.left, y: e.clientY - rect.top };
+			return;
+		}
+	}
+
+	function handlePointerUp(e: PointerEvent) {
+		if (isPanning) {
+			isPanning = false;
+			return;
+		}
+
+		if (isDragging) {
+			isDragging = false;
+			dragTargetId = null;
+			return;
+		}
+
+		if (isLassoing && lassoRect) {
+			// Select objects within lasso (in screen space)
+			const newSelection = new Set(selectedIds);
+			for (const obj of visibleObjs) {
+				const screenPos = {
+					x: obj.x * camera.zoom + camera.x,
+					y: obj.y * camera.zoom + camera.y,
+					width: obj.width * camera.zoom,
+					height: obj.height * camera.zoom,
+				};
+				// Check if object intersects lasso rect
+				if (
+					screenPos.x < lassoRect.x + lassoRect.width &&
+					screenPos.x + screenPos.width > lassoRect.x &&
+					screenPos.y < lassoRect.y + lassoRect.height &&
+					screenPos.y + screenPos.height > lassoRect.y
+				) {
+					newSelection.add(obj.id);
+				}
+			}
+			selectedIds = newSelection;
+			onSelectionChange?.([...selectedIds]);
+			isLassoing = false;
+			return;
+		}
+	}
+
+	// --- Touch: pinch-zoom and two-finger pan ---
+	function handleTouchStart(e: TouchEvent) {
+		for (const touch of e.changedTouches) {
+			activeTouches.set(touch.identifier, { x: touch.clientX, y: touch.clientY });
+		}
+		if (activeTouches.size === 2) {
+			const [a, b] = [...activeTouches.values()];
+			lastPinchDist = Math.hypot(b.x - a.x, b.y - a.y);
+			lastPinchCenter = { x: (a.x + b.x) / 2, y: (a.y + b.y) / 2 };
+			e.preventDefault();
+		}
+	}
+
+	function handleTouchMove(e: TouchEvent) {
+		for (const touch of e.changedTouches) {
+			activeTouches.set(touch.identifier, { x: touch.clientX, y: touch.clientY });
+		}
+		if (activeTouches.size === 2) {
+			const [a, b] = [...activeTouches.values()];
+			const dist = Math.hypot(b.x - a.x, b.y - a.y);
+			const center = { x: (a.x + b.x) / 2, y: (a.y + b.y) / 2 };
+
+			// Pinch zoom
+			if (lastPinchDist > 0) {
+				const factor = dist / lastPinchDist;
+				zoomAt(center.x, center.y, factor);
+			}
+
+			// Two-finger pan
+			const dx = center.x - lastPinchCenter.x;
+			const dy = center.y - lastPinchCenter.y;
+			camera = { ...camera, x: camera.x + dx, y: camera.y + dy };
+
+			lastPinchDist = dist;
+			lastPinchCenter = center;
+			e.preventDefault();
+		}
+	}
+
+	function handleTouchEnd(e: TouchEvent) {
+		for (const touch of e.changedTouches) {
+			activeTouches.delete(touch.identifier);
+		}
+		if (activeTouches.size < 2) {
+			lastPinchDist = 0;
+		}
+	}
+
+	// --- Fullscreen ---
+	function toggleFullscreen() {
+		isFullscreen = !isFullscreen;
+	}
+
+	// --- Public API via bindable ---
+	export function getCamera(): Camera {
+		return { ...camera };
+	}
+
+	export function setCamera(cam: Camera) {
+		camera = { ...cam, zoom: clampZoom(cam.zoom) };
+	}
+
+	export function zoomToFit(padding: number = 50) {
+		if (objects.length === 0) return;
+		let minX = Infinity, minY = Infinity, maxX = -Infinity, maxY = -Infinity;
+		for (const obj of objects) {
+			minX = Math.min(minX, obj.x);
+			minY = Math.min(minY, obj.y);
+			maxX = Math.max(maxX, obj.x + obj.width);
+			maxY = Math.max(maxY, obj.y + obj.height);
+		}
+		const contentW = maxX - minX;
+		const contentH = maxY - minY;
+		if (contentW <= 0 || contentH <= 0) return;
+
+		const zoomX = (viewport.width - padding * 2) / contentW;
+		const zoomY = (viewport.height - padding * 2) / contentH;
+		const zoom = clampZoom(Math.min(zoomX, zoomY));
+
+		camera = {
+			x: (viewport.width - contentW * zoom) / 2 - minX * zoom,
+			y: (viewport.height - contentH * zoom) / 2 - minY * zoom,
+			zoom,
+		};
+	}
+</script>
+
+<!-- svelte-ignore a11y_no_static_element_interactions -->
+<div
+	bind:this={containerEl}
+	class="canvas-container"
+	class:canvas-fullscreen={isFullscreen}
+	class:canvas-panning={isPanning || spaceHeld}
+	onwheel={handleWheel}
+	onpointerdown={handlePointerDown}
+	onpointermove={handlePointerMove}
+	onpointerup={handlePointerUp}
+	ontouchstart={handleTouchStart}
+	ontouchmove={handleTouchMove}
+	ontouchend={handleTouchEnd}
+	role="application"
+	aria-label="Canvas"
+>
+	<!-- Toolbar -->
+	<div class="canvas-toolbar">
+		<button
+			class="canvas-toolbar-btn"
+			onclick={() => zoomAt(viewport.width / 2, viewport.height / 2, 1.2)}
+			title="Zoom inn"
+			aria-label="Zoom inn"
+		>+</button>
+		<span class="canvas-toolbar-zoom">{Math.round(camera.zoom * 100)}%</span>
+		<button
+			class="canvas-toolbar-btn"
+			onclick={() => zoomAt(viewport.width / 2, viewport.height / 2, 0.8)}
+			title="Zoom ut"
+			aria-label="Zoom ut"
+		>−</button>
+		<button
+			class="canvas-toolbar-btn"
+			onclick={() => zoomToFit()}
+			title="Tilpass visning"
+			aria-label="Tilpass visning"
+		>⊡</button>
+		<div class="canvas-toolbar-sep"></div>
+		<button
+			class="canvas-toolbar-btn"
+			class:canvas-toolbar-active={grid.enabled}
+			onclick={() => (grid = { ...grid, enabled: !grid.enabled })}
+			title="Snap-to-grid (G)"
+			aria-label="Snap-to-grid"
+		>#</button>
+		<button
+			class="canvas-toolbar-btn"
+			onclick={toggleFullscreen}
+			title="Fullskjerm"
+			aria-label="Fullskjerm"
+		>{isFullscreen ? '⊖' : '⊕'}</button>
+	</div>
+
+	<!-- Grid background (when enabled) -->
+	{#if grid.enabled}
+		<div
+			class="canvas-grid"
+			style:background-size="{grid.size * camera.zoom}px {grid.size * camera.zoom}px"
+			style:background-position="{camera.x}px {camera.y}px"
+		></div>
+	{/if}
+
+	<!-- World layer — CSS transformed -->
+	<div
+		class="canvas-world"
+		style:transform={transformStyle}
+	>
+		{#each visibleObjs as obj (obj.id)}
+			<div
+				class="canvas-object"
+				class:canvas-object-selected={selectedIds.has(obj.id)}
+				data-canvas-object-id={obj.id}
+				style:left="{obj.x}px"
+				style:top="{obj.y}px"
+				style:width="{obj.width}px"
+				style:height="{obj.height}px"
+			>
+				{@render renderObject(obj)}
+			</div>
+		{/each}
+	</div>
+
+	<!-- Lasso selection overlay (screen space) -->
+	{#if isLassoing && lassoRect}
+		<div
+			class="canvas-lasso"
+			style:left="{lassoRect.x}px"
+			style:top="{lassoRect.y}px"
+			style:width="{lassoRect.width}px"
+			style:height="{lassoRect.height}px"
+		></div>
+	{/if}
+
+	<!-- Mobile: touch hint -->
+	{#if viewport.width < 768}
+		<div class="canvas-touch-hint">
+			Bruk to fingre for å panorere og zoome
+		</div>
+	{/if}
+</div>
+
+<style>
+	.canvas-container {
+		position: relative;
+		width: 100%;
+		height: 100%;
+		overflow: hidden;
+		background: #f8f9fa;
+		touch-action: none; /* We handle all touch ourselves */
+		user-select: none;
+		cursor: default;
+	}
+
+	.canvas-container.canvas-panning {
+		cursor: grab;
+	}
+
+	.canvas-container.canvas-fullscreen {
+		position: fixed;
+		inset: 0;
+		z-index: 50;
+		background: #f8f9fa;
+	}
+
+	.canvas-world {
+		position: absolute;
+		top: 0;
+		left: 0;
+		transform-origin: 0 0;
+		will-change: transform;
+	}
+
+	.canvas-object {
+		position: absolute;
+		cursor: default;
+	}
+
+	.canvas-object-selected {
+		outline: 2px solid #3b82f6;
+		outline-offset: 2px;
+		border-radius: 4px;
+	}
+
+	/* Grid pattern */
+	.canvas-grid {
+		position: absolute;
+		inset: 0;
+		pointer-events: none;
+		background-image:
+			linear-gradient(to right, rgba(0,0,0,0.05) 1px, transparent 1px),
+			linear-gradient(to bottom, rgba(0,0,0,0.05) 1px, transparent 1px);
+	}
+
+	/* Lasso */
+	.canvas-lasso {
+		position: absolute;
+		border: 1px dashed #3b82f6;
+		background: rgba(59, 130, 246, 0.08);
+		pointer-events: none;
+		z-index: 10;
+	}
+
+	/* Toolbar */
+	.canvas-toolbar {
+		position: absolute;
+		bottom: 12px;
+		left: 50%;
+		transform: translateX(-50%);
+		z-index: 20;
+		display: flex;
+		align-items: center;
+		gap: 4px;
+		padding: 4px 8px;
+		background: white;
+		border: 1px solid #e5e7eb;
+		border-radius: 8px;
+		box-shadow: 0 1px 3px rgba(0,0,0,0.1);
+	}
+
+	.canvas-toolbar-btn {
+		display: flex;
+		align-items: center;
+		justify-content: center;
+		width: 32px;
+		height: 32px;
+		border: none;
+		background: transparent;
+		border-radius: 6px;
+		cursor: pointer;
+		font-size: 16px;
+		color: #374151;
+		transition: background 0.15s;
+	}
+
+	.canvas-toolbar-btn:hover {
+		background: #f3f4f6;
+	}
+
+	.canvas-toolbar-active {
+		background: #eff6ff;
+		color: #3b82f6;
+	}
+
+	.canvas-toolbar-zoom {
+		font-size: 12px;
+		color: #6b7280;
+		min-width: 40px;
+		text-align: center;
+		font-variant-numeric: tabular-nums;
+	}
+
+	.canvas-toolbar-sep {
+		width: 1px;
+		height: 20px;
+		background: #e5e7eb;
+		margin: 0 4px;
+	}
+
+	/* Touch hint for mobile */
+	.canvas-touch-hint {
+		position: absolute;
+		top: 12px;
+		left: 50%;
+		transform: translateX(-50%);
+		z-index: 20;
+		padding: 4px 12px;
+		background: rgba(0,0,0,0.6);
+		color: white;
+		font-size: 12px;
+		border-radius: 16px;
+		pointer-events: none;
+		opacity: 0.8;
+	}
+
+	/* Responsive touch targets */
+	@media (max-width: 768px) {
+		.canvas-toolbar-btn {
+			width: 44px;
+			height: 44px;
+			font-size: 20px;
+		}
+
+		.canvas-toolbar {
+			bottom: 16px;
+			gap: 2px;
+			padding: 4px;
+		}
+	}
+
+	@media (min-width: 768px) and (max-width: 1024px) {
+		.canvas-toolbar-btn {
+			width: 38px;
+			height: 38px;
+		}
+	}
+</style>

frontend/src/lib/components/canvas/index.ts

@@ -0,0 +1,2 @@
+export { default as Canvas } from './Canvas.svelte';
+export * from './types.js';

frontend/src/lib/components/canvas/types.ts

@@ -0,0 +1,121 @@
+/**
+ * Canvas Primitive — shared types for the freeform canvas component.
+ * Used by whiteboard, storyboard, and future canvas-based views.
+ */
+
+/** Camera state: 2D affine transformation */
+export interface Camera {
+	x: number;      // pan offset X (world coords)
+	y: number;      // pan offset Y (world coords)
+	zoom: number;   // scale factor (1.0 = 100%)
+}
+
+/** Generic canvas object — consumer determines rendering */
+export interface CanvasObject {
+	id: string;
+	x: number;
+	y: number;
+	width: number;
+	height: number;
+}
+
+/** Axis-aligned bounding box for intersection tests */
+export interface Rect {
+	x: number;
+	y: number;
+	width: number;
+	height: number;
+}
+
+/** Events emitted by the canvas for consumer integration (e.g. SpacetimeDB sync) */
+export interface CanvasEvents {
+	onObjectMove?: (id: string, x: number, y: number) => void;
+	onObjectResize?: (id: string, w: number, h: number) => void;
+	onCameraChange?: (camera: Camera) => void;
+	onSelectionChange?: (ids: string[]) => void;
+}
+
+/** Snap-to-grid configuration */
+export interface GridConfig {
+	enabled: boolean;
+	size: number; // grid cell size in world pixels (default 20)
+}
+
+/** Viewport size in screen pixels */
+export interface ViewportSize {
+	width: number;
+	height: number;
+}
+
+// --- Utility functions ---
+
+/** Snap a value to the nearest grid point */
+export function snap(value: number, gridSize: number): number {
+	return Math.round(value / gridSize) * gridSize;
+}
+
+/** Convert screen coordinates to world coordinates */
+export function screenToWorld(screenX: number, screenY: number, camera: Camera): { x: number; y: number } {
+	return {
+		x: (screenX - camera.x) / camera.zoom,
+		y: (screenY - camera.y) / camera.zoom,
+	};
+}
+
+/** Convert world coordinates to screen coordinates */
+export function worldToScreen(worldX: number, worldY: number, camera: Camera): { x: number; y: number } {
+	return {
+		x: worldX * camera.zoom + camera.x,
+		y: worldY * camera.zoom + camera.y,
+	};
+}
+
+/** Get the visible world-space rectangle for the current viewport */
+export function getVisibleWorldRect(camera: Camera, viewport: ViewportSize): Rect {
+	const topLeft = screenToWorld(0, 0, camera);
+	const bottomRight = screenToWorld(viewport.width, viewport.height, camera);
+	return {
+		x: topLeft.x,
+		y: topLeft.y,
+		width: bottomRight.x - topLeft.x,
+		height: bottomRight.y - topLeft.y,
+	};
+}
+
+/** Check if two rectangles intersect */
+export function intersects(a: Rect, b: Rect): boolean {
+	return (
+		a.x < b.x + b.width &&
+		a.x + a.width > b.x &&
+		a.y < b.y + b.height &&
+		a.y + a.height > b.y
+	);
+}
+
+/** Filter objects to only those visible in the viewport (with margin for smooth scrolling) */
+export function visibleObjects<T extends CanvasObject>(
+	objects: T[],
+	camera: Camera,
+	viewport: ViewportSize,
+	margin: number = 200
+): T[] {
+	const worldRect = getVisibleWorldRect(camera, viewport);
+	// Expand by margin in world space
+	const expanded: Rect = {
+		x: worldRect.x - margin,
+		y: worldRect.y - margin,
+		width: worldRect.width + margin * 2,
+		height: worldRect.height + margin * 2,
+	};
+	return objects.filter(obj =>
+		intersects({ x: obj.x, y: obj.y, width: obj.width, height: obj.height }, expanded)
+	);
+}
+
+/** Clamp zoom to allowed range */
+export const ZOOM_MIN = 0.1;
+export const ZOOM_MAX = 3.0;
+
+export function clampZoom(zoom: number): number {
+	return Math.min(ZOOM_MAX, Math.max(ZOOM_MIN, zoom));
+}

tasks.md

@@ -212,8 +212,7 @@ Ref: `docs/features/ai_verktoy.md`, `docs/retninger/arbeidsflaten.md`
 
 Ref: `docs/retninger/arbeidsflaten.md`, `docs/features/canvas_primitiv.md`
 
-- [~] 19.1 Canvas-primitiv Svelte-komponent: pan/zoom kamera med CSS transforms, viewport culling, pointer events (mus + touch), snap-to-grid (valgfritt), fullskjermsmodus. Ref: `docs/features/canvas_primitiv.md`.
-  > Påbegynt: 2026-03-18T07:13
+- [x] 19.1 Canvas-primitiv Svelte-komponent: pan/zoom kamera med CSS transforms, viewport culling, pointer events (mus + touch), snap-to-grid (valgfritt), fullskjermsmodus. Ref: `docs/features/canvas_primitiv.md`.
 - [ ] 19.2 BlockShell wrapper-komponent: header med tittel + fullskjerm/resize/lukk-knapper, drag-handles for repositionering, resize-handles, drop-sone rendering (highlight ved drag-over). Responsivt (min-size, max-size).
 - [ ] 19.3 Arbeidsflaten layout: skriv om `/collection/[id]` fra vertikal stack til Canvas + BlockShell. Last brukerens lagrede arrangement eller bruk defaults fra samlingens traits. Persist arrangement i bruker-edge metadata. Desktop: spatial canvas, mobil: stacked/tabs. Ref: `docs/retninger/arbeidsflaten.md` § "Tre lag".
 - [ ] 19.4 Kontekst-header: header tilhører flaten, viser gjeldende node som nedtrekksmeny/kontekst-velger. Mest brukte noder øverst (frekvens/recency), søkbart. Verktøymeny for å instansiere nye paneler. Ref: `docs/retninger/arbeidsflaten.md` § "Kontekst-header".